style: enforce coding standard — headers, @brief on #define, Doxygen on statics, remove _ prefix, max 8 lines per function

0x0014_static-variables/0x0014_static-variables.c

@@ -1,31 +1,90 @@
+/**
+ * @file 0x0014_static-variables.c
+ * @brief Static variables: compare regular vs static local variable persistence
+ * @author Kevin Thomas
+ * @date 2025
+ *
+ * MIT License
+ *
+ * Copyright (c) 2025 Kevin Thomas
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * -----------------------------------------------------------------------------
+ *
+ * Demonstrates the difference between regular and static local variables.
+ * A regular variable resets to 42 each iteration while a static variable
+ * persists and increments across loop iterations. Also reads a button on
+ * GPIO15 and mirrors its state to an LED on GPIO16.
+ *
+ * Wiring:
+ *   GPIO15 -> Button (with pull-up, active low)
+ *   GPIO16 -> LED anode (with current-limiting resistor to GND)
+ */
+
 #include <stdio.h>
 #include "pico/stdlib.h"
 
-int main(void) {
-    stdio_init_all();
-
-    const uint BUTTON_GPIO = 15;
-    const uint LED_GPIO = 16;
-    bool pressed = 0;
+/** @brief GPIO pin number for the button input */
+#define BUTTON_GPIO 15
+/** @brief GPIO pin number for the LED output */
+#define LED_GPIO    16
 
+/**
+ * @brief Initialize button and LED GPIO pins
+ *
+ * @details Configures the button pin as input with pull-up and the
+ *          LED pin as output.
+ *
+ * @retval None
+ */
+static void init_gpio(void) {
     gpio_init(BUTTON_GPIO);
     gpio_set_dir(BUTTON_GPIO, GPIO_IN);
     gpio_pull_up(BUTTON_GPIO);
-
     gpio_init(LED_GPIO);
     gpio_set_dir(LED_GPIO, GPIO_OUT);
+}
 
+/**
+ * @brief Print and increment regular vs static variables, update LED
+ *
+ * @details Prints both variable values, increments them, reads the
+ *          button state and drives the LED accordingly.
+ *
+ * @retval None
+ */
+static void demo_static_variable(void) {
+    uint8_t regular_fav_num = 42;
+    static uint8_t static_fav_num = 42;
+    printf("regular_fav_num: %d\r\n", regular_fav_num);
+    printf("static_fav_num: %d\r\n", static_fav_num);
+    regular_fav_num++;
+    static_fav_num++;
+    bool pressed = gpio_get(BUTTON_GPIO);
+    gpio_put(LED_GPIO, pressed ? 0 : 1);
+}
+
+int main(void) {
+    stdio_init_all();
+    init_gpio();
     while (true) {
-        uint8_t regular_fav_num = 42;
-        static uint8_t static_fav_num = 42;
-        
-        printf("regular_fav_num: %d\r\n", regular_fav_num);
-        printf("static_fav_num: %d\r\n", static_fav_num);
-        
-        regular_fav_num++;
-        static_fav_num++;
-        
-        pressed = gpio_get(BUTTON_GPIO);
-        gpio_put(LED_GPIO, pressed ? 0 : 1);
+        demo_static_variable();
     }
 }